Task_scheduling_test.cpp

#include <omp.h>
#include <iostream>
#include <sstream>

#define NUMBER 1000000000
static double init;
static int limit = 32;
static std::string color[4] = {"white","cyan","yellow","green"};

inline double get_time(){
    return omp_get_wtime() - init;
}

inline std::string name(int num, int cpu){
    std::stringstream ss;
    ss << "\"" << num << " (" << cpu << ")\"";
    return ss.str();
}

int fib(int num){

    int p = omp_get_thread_num();
    #pragma omp critical
    std::cout << name(num, p) << " [fillcolor=" << color[omp_get_thread_num()] << "]" << std::endl;

    int a = 0, b = 0;

    //left child
    if (num*2 < limit)
    {
        #pragma omp task shared(a,p,num)
        {
            double t = get_time();
            #pragma omp critical
            std::cout << name(num, p) << " -> " << name(num*2, omp_get_thread_num()) << " [label=" << t << "]" << std::endl;
            a = fib(num*2);
        }
    }
    //right child
    if (num*2 + 1 < limit){
        #pragma omp task shared(b,p,num)
        {
            double t = get_time();
            #pragma omp critical
            std::cout << name(num, p) << " -> " << name(num*2+1, omp_get_thread_num()) << " [label=" << t << "]" << std::endl;
            b = fib(num*2+1);
        }
    }

    // waste some time
    int c = 0;
    for(int i=0; i<NUMBER * num; i++)
        c += i/num;

    #pragma omp taskwait

    return a+b+c;
}

int main(){
    init = omp_get_wtime();
    int a;
    std::cout << "digraph {\nnode [shape=circle, style=\"filled\"]" << std::endl;
    #pragma omp parallel shared(a)
    #pragma omp single
    a = fib(1);
    std::cout << "}" << std::endl;
    std::cerr << a << std::endl;
    return 0;
}